There are conventionally known sleep determination apparatuses for determining whether a subject is asleep or not based on an output signal (a body movement signal) obtained by detecting body movement of the subject. For example, Patent Document 1 discloses a sleep determination apparatus which determines that a subject is in a hypnagogic state when an output signal obtained by detecting the subject's body movement continuously remains between a first threshold and a second threshold for a predetermined time.
Patent Document 1: Published Japanese Patent No. 2817358